Methods for synthesizing and purifying aminoalkyl tetracycline compounds

Abstract

Methods for the synthesis and purification of 9-amino alkyl tetracycline compounds are described.

The invention claimed is: 
     
       1. A method of purifying an alkylaminomethyl minocycline compound, comprising:
 a) injecting a low pH aqueous solution of said alkylaminomethyl minocycline compound into a liquid chromatography device in a polar organic solvent gradient, and combining the product fractions; 
 b) adjusting the pH of said product fractions to 4.0-4.5; 
 c) washing said product fractions with a first non-polar organic solvent to form a first organic layer and a first aqueous layer, and discarding said first organic layer; 
 d) adjusting the pH of said first aqueous layer to 7.5-8.5; and 
 e) washing said first aqueous layer with a second non-polar organic solvent to form a second organic layer and a second aqueous layer, and discarding said second aqueous layer, 
 such that said alkylaminomethyl minocycline compound is purified. 
 
     
     
       2. The method of  claim 1 , wherein said low pH aqueous solution has a pH of 2-3. 
     
     
       3. The method of  claim 1 , wherein said low pH aqueous solution comprises methyl sulfonic acid. 
     
     
       4. The method of  claim 1 , wherein said polar organic solvent is acetonitrile. 
     
     
       5. The method of  claim 1 , wherein said pH in step b) or d) is adjusted with a base. 
     
     
       6. The method of  claim 5 , wherein said base is selected from the group consisting of metal hydroxide, metal carbonate, metal bicarbonate, ammonia, organic primary amine, organic secondary amine and organic tertiary amine. 
     
     
       7. The method of  claim 6 , wherein said metal is selected from the group consisting of lithium, sodium, potassium, calcium, magnesium and aluminum. 
     
     
       8. The method of  claim 6 , wherein said base is sodium hydroxide or ammonia. 
     
     
       9. The method of  claim 1 , wherein said first non-polar organic solvent is methylene chloride. 
     
     
       10. The method of  claim 1 , wherein said first organic layer comprises by-products, hydrophobic impurities and oxidative degradents of said alkylaminomethyl minocycline compound. 
     
     
       11. The method of  claim 1 , wherein said second non-polar organic solvent is methylene chloride. 
     
     
       12. The method of  claim 1 , wherein said second aqueous layer comprises by-products and β epimer of said alkylaminomethyl minocycline compound. 
     
     
       13. The method of  claim 1 , wherein an antioxidant is added. 
     
     
       14. The method of  claim 13 , wherein said antioxidant is ammonium sulfite, sodium sulfite, bisulfite or meta bisulfite. 
     
     
       15. The method of  claim 1 , wherein said alkylaminomethyl minocycline compound is: 
       
         
           
           
               
               
           
         
         wherein R A  is alkyl, and R B  is hydrogen or alkyl. 
       
     
     
       16. The method of  claim 15 , wherein R B  is hydrogen. 
     
     
       17. The method of  claim 16 , wherein R A  is alkyl. 
     
     
       18. The method of  claim 17 , wherein said alkyl is (CH 3 ) 3 CCH 2 -. 
     
     
       19. The method of  claim 1 , wherein said alkylaminomethyl minocycline compound is: 
       
         
           
           
               
               
           
         
       
     
     
       20. The method of  claim 1 , wherein hydrophobic impurities and oxidative degradents are removed from said alkylaminomethyl minocycline compound. 
     
     
       21. The method of  claim 1 , wherein by-products and β-C-4 epimer are removed from said alkylaminomethyl minocycline compound. 
     
     
       22. The method of  claim 1 , wherein said alkylaminomethyl minocycline compound is essentially free of hydrophobic impurities and oxidative degradents. 
     
     
       23. The method of  claim 1 , wherein said alkylaminomethyl minocycline compound is essentially free of by-products, β-C-4 epimer, hydrophobic impourities and oxidative degradents. 
     
     
       24. The method of  claim 1 , wherein said alkylaminomethyl minocycline compound comprises at least 50% α-C-4 epimer. 
     
     
       25. The method of  claim 24 , wherein said alkylaminomethyl minocycline compound comprises at least 95% α-C-4 epimer. 
     
     
       26. The method of  claim 25 , wherein said alkylaminomethyl minocycline compound comprises at least 99.9% α-C-4 epimer. 
     
     
       27. The method of  claim 1 , wherein said alkylaminomethyl minocycline compound comprises less than 7% β-C-4 epimer. 
     
     
       28. The method of  claim 27 , wherein said alkylaminomethyl minocycline compound comprises less than 3% β-C-4 epimer.